Autostereoscopic display device

ABSTRACT

An autostereoscopic display device uses an electroluminescent display. A set of pixels is provided beneath view forming elements (such as lenses), with a plurality of pixels across the view forming element width direction. The pixels are arranged with at least two different angular orientations with respect to the substrate. The out-coupling performance is improved by arranging for the light emission direction to be substantially perpendicular to the desired emitting surface of the view forming elements.

CROSS-REFERENCE TO PRIOR APPLICATIONS

This application a continuation of U.S. patent application Ser. No.14/442,829, filed on May 14, 2015, which is U.S. National Phaseapplication under 35 U.S.C. §371 of International Application No.PCT/IB2013/058273, filed on Sep. 4, 2013, which claims the benefit ofU.S. Patent Application No. 61/727,311, filed on Nov. 16, 2012. Theseapplications are hereby incorporated by reference herein.

FIELD OF THE INVENTION

This invention relates to an autostereoscopic display device of the typethat comprises a display panel having an array of display pixels forproducing a display and an imaging arrangement for directing differentviews to different spatial positions.

BACKGROUND OF THE INVENTION

A first example of an imaging arrangement for use in this type ofdisplay is a barrier, for example with slits that are sized andpositioned in relation to the underlying pixels of the display. In atwo-view design, the viewer is able to perceive a 3D image if his/herhead is at a fixed position. The barrier is positioned in front of thedisplay panel and is designed so that light from the odd and even pixelcolumns is directed towards the left and right eye of the viewer,respectively.

A drawback of this type of two-view display design is that the viewerhas to be at a fixed position, and can only move approximately 3 cm tothe left or right. In a more preferred embodiment there are not twosub-pixel columns beneath each slit, but several. In this way, theviewer is allowed to move to the left and right and perceive a stereoimage in his/her eyes all the time.

The barrier arrangement is simple to produce but is not light efficient.A preferred alternative is therefore to use a lens arrangement as theimaging arrangement. For example, an array of elongate lenticularelements can be provided extending parallel to one another and overlyingthe display pixel array, and the display pixels are observed throughthese lenticular elements.

The lenticular elements are provided as a sheet of elements, each ofwhich comprises an elongate semi-cylindrical lens element. Thelenticular elements extend in the column direction of the display panel,with each lenticular element overlying a respective group of two or moreadjacent columns of display pixels.

In an arrangement in which each lenticule is associated with two columnsof display pixels, the display pixels in each column provide a verticalslice of a respective two dimensional sub-image. The lenticular sheetdirects these two slices and corresponding slices from the display pixelcolumns associated with the other lenticules, to the left and right eyesof a user positioned in front of the sheet, so that the user observes asingle stereoscopic image. The sheet of lenticular elements thusprovides a light output directing function.

In other arrangements, each lenticule is associated with a group of fouror more adjacent display pixels in the row direction. Correspondingcolumns of display pixels in each group are arranged appropriately toprovide a vertical slice from a respective two dimensional sub-image. Asa user's head is moved from left to right, a series of successive,different, stereoscopic views are perceived creating, for example, alook-around impression.

Known autostereoscopic displays use liquid crystal displays to generatethe image.

There is increasing interest in the use of organic light emitting diode(OLED) displays generally, as these do not need polarizers, andpotentially they should be able to offer increased efficiency since thepixels are turned off when not used to display an image, compared to LCDpanels which use a continuously illuminated backlight. However, thesedisplay pixels emit light in a wide range of directions, and in 3Ddisplays this presents a particular problem of cross talk.

This invention is based on the use of an OLED or other thin filmemissive display such as an electroluminescent display within anautostereoscopic display system, and makes use of the additional designflexibility offered by these displays, in order to address the problemof cross talk between views in a 3D lenticular display.

SUMMARY OF THE INVENTION

The invention is defined by the independent claims. Further features aredefined in the dependent claims.

According to the invention, there is provided an autostereoscopicdisplay device comprising:

an electroluminescent display arrangement comprising an array of spacedpixels over a substrate each having a light output surface;

an autostereoscopic view forming arrangement comprising a set of viewforming elements over the display arrangement,

wherein a set of pixels is provided beneath each view forming elementwith at least two pixels across the view forming element widthdirection, wherein the pixels across the view forming element widthdirection are arranged with at least two different angular orientationsof their light output surface with respect to the substrate.

The OLED emitters are thus parallel to a tilted surface, such that theOLED emits light centred around a direction which is not perpendicularto the display, the emission direction being different for differentOLED pixels. In this manner, the out-coupling performance is improved byarranging for the light emission direction to be substantiallyperpendicular to the desired emitting surface of the view formingarrangement (such as a microlens or lenticular lens array). The approachalso results in a reduction of crosstalk between different views, asthese become more separated in angle by the tilting.

The angle of tilt is preferably in a plane perpendicular to the displaysubstrate plane and parallel to the view forming element width direction(i.e. in a vertical slice through the display across the widthdirection).

In the case of elongate lenticular lenses, the lens elongate axisdirection remains parallel to the plane of the light output surface, sothat the angle of tilt can be considered as a tilt about the elongatelens axis. The light output surfaces are thus tilted in a way whichgenerally corresponds to (or mirrors) the shape of the lens surface.

The lenticular lenses preferably extend in a pixel column direction orare inclined at an acute angle to the pixel column direction, whereineach lens covers a plurality of pixel columns.

The electroluminescent display arrangement can comprise an array ofreflective anodes over the substrate, an array of electroluminescentlayer portions over the anodes, and an array of transparent cathodesover the electroluminescent layer portions. This defines a top emittingstructure. In this case, the electroluminescent portions are between thesubstrate and the lens arrangement.

Instead, the electroluminescent display arrangement can comprise anarray of transparent anodes over the substrate, an array ofelectroluminescent layer portions over the anodes, and an array ofreflective cathodes over the electroluminescent layer portions. Thisdefines a bottom emitting structure. In this case, the substrate isbetween the electroluminescent portions and the lens arrangement.

In further embodiments both the anode and the cathode may be at leastpartially transparent, resulting in a transparent electroluminescentemitting structure.

The substrate can be planar and the device can then comprise spacersbetween at least some of the pixels and the substrate to define thedifferent angular orientations. Different pixel heights can also beprovided by the spacers with respect to the substrate, so that allpixels lie at the focal surface of the lenses.

Alternatively, the substrate can have a non-planar shape thereby todefine the different orientations, and again optionally with desireddifferent heights.

The invention also provides a method of displaying autostereoscopicimages, comprising:

generating a pixelated image using an electroluminescent displayarrangement comprising an array of spaced pixels over a substrate; and

directing different sub-images to different directions using a viewforming arrangement comprising a set of view forming elements over thedisplay arrangement, wherein a set of pixels is provided beneath eachview forming element each having a light output surface, with at leasttwo pixels across the view forming element width direction,

wherein the method further comprises positioning the pixels across theview forming element width direction with at least two different angularorientations of their light output surface with respect to thesubstrate.

The invention also provides a method manufacturing an autostereoscopicdisplay device, comprising:

forming an electroluminescent display arrangement comprising an array ofspaced pixels over a substrate;

providing a view forming arrangement comprising a plurality of viewforming elements over the display arrangement, wherein a set of pixelsis provided beneath each view forming element each having a light outputsurface, with at least two pixels across the view forming element widthdirection,

wherein the method comprises arranging the pixels across the viewforming element width direction with at least two different angularorientations of their light output surface with respect to thesubstrate.

The different angular orientations are provided by:

providing spacers between at least some of the pixels and a planarsubstrate; or

forming the electroluminescent display arrangement over a contouredsubstrate; or

forming the electroluminescent display arrangement over a planarsubstrate and subsequently forming a contour.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention will now be described, purely by way ofexample, with reference to the accompanying drawings, in which:

FIG. 1 is a schematic perspective view of a known autostereoscopicdisplay device;

FIG. 2 shows how a lenticular array provides different views todifferent spatial locations;

FIG. 3 schematically shows the structure of a single pixel of an OLEDdisplay, and in the form of a backward emitting structure;

FIG. 4 is used to explain the problem of forming a lenticular over anelectroluminescent display panel.

FIG. 5 shows a first example of pixel structure in accordance with theinvention;

FIG. 6 shows a second example of pixel structure in accordance with theinvention;

FIG. 7 shows a third example of pixel structure in accordance with theinvention;

FIG. 8 shows a fourth example of pixel structure in accordance with theinvention; and

FIG. 9 is used to explain how the views in secondary cones can beaffected.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The invention provides an autostereoscopic display device using anelectroluminescent display, wherein a set of pixels is provided beneatha view forming arrangement, with a plurality of pixels across the viewforming element width direction. The pixels across the width directionare arranged with at least two different angular orientations withrespect to the substrate. This enables the pixels output surfaces todefine a non-planar array, and they can follow the area to which lightis focused by the lenticular lenses.

Before describing the invention, the basic operation of a known 3Dautostereoscopic display will first be described.

FIG. 1 is a schematic perspective view of a known direct viewautostereoscopic display device 1 using an LCD panel to generate theimages. The known device 1 comprises a liquid crystal display panel 3 ofthe active matrix type that acts as a spatial light modulator to producethe display.

The display panel 3 has an orthogonal array of display pixels 5 arrangedin rows and columns. For the sake of clarity, only a small number ofdisplay pixels 5 are shown in the Figure. In practice, the display panel3 might comprise about one thousand rows and several thousand columns ofdisplay pixels 5.

The structure of the liquid crystal display panel 3 as commonly used inautostereoscopic displays is entirely conventional. In particular, thepanel 3 comprises a pair of spaced transparent glass substrates, betweenwhich an aligned twisted nematic or other liquid crystal material isprovided. The substrates carry patterns of transparent indium tin oxide(ITO) electrodes on their facing surfaces. Polarising layers are alsoprovided on the outer surfaces of the substrates.

Each display pixel 5 comprises opposing electrodes on the substrates,with the intervening liquid crystal material therebetween. The shape andlayout of the display pixels 5 are determined by the shape and layout ofthe electrodes. The display pixels 5 are regularly spaced from oneanother by gaps.

Each display pixel 5 is associated with a switching element, such as athin film transistor (TFT) or thin film diode (TFD). The display pixelsare operated to produce the display by providing addressing signals tothe switching elements, and suitable addressing schemes will be known tothose skilled in the art.

The display panel 3 is illuminated by a light source 7 comprising, inthis case, a planar backlight extending over the area of the displaypixel array. Light from the light source 7 is directed through thedisplay panel 3, with the individual display pixels 5 being driven tomodulate the light and produce the display.

The display device 1 also comprises a lenticular sheet 9, arranged overthe display side of the display panel 3, which performs a view formingfunction. The lenticular sheet 9 comprises a row of lenticular elements11 extending parallel to one another, of which only one is shown withexaggerated dimensions for the sake of clarity.

The lenticular elements 11 are in the form of convex cylindrical lenses,and they act as a light output directing means to provide differentimages, or views, from the display panel 3 to the eyes of a userpositioned in front of the display device 1.

The device has a controller 13 which controls the backlight and thedisplay panel.

The autostereoscopic display device 1 shown in FIG. 1 is capable ofproviding several different perspective views in different directions.In particular, each lenticular element 11 overlies a small group ofdisplay pixels 5 in each row. The lenticular element 11 projects eachdisplay pixel 5 of a group in a different direction, so as to form theseveral different views. As the user's head moves from left to right,his/her eyes will receive different ones of the several views, in turn.

In the case of an LCD panel, a light polarising means must also be usedin conjunction with the above described array, since the liquid crystalmaterial is birefringent, with the refractive index switching onlyapplying to light of a particular polarisation. The light polarisingmeans may be provided as part of the display panel or the imagingarrangement of the device.

FIG. 2 shows the principle of operation of a lenticular type imagingarrangement as described above and shows the backlight 20, displaydevice 24 such as an LCD and the lenticular array 28. FIG. 2 shows howthe lenticular arrangement 28 directs different pixel outputs to threedifferent spatial locations 22′, 22″, 22′″. These locations are all in aso-called viewing cone, in which all views are different. The views arerepeated in other viewing cones, which are generated by pixel lightpassing through adjacent lenses. The spatial locations 23′, 23″, 23′″are in the next viewing cone.

The invention is based on the use of an electroluminescent displaytechnology, such as an OLED display, instead of the LCD display shown inFIGS. 1 and 2. The use of an

OLED display avoids the need for a separate backlight and polarizers.OLED promises to be the display technology of the future.

OLED displays differ significantly from LCD displays in how the light isemitted from the pixel. OLED pixels are diffuse emitters that emit lightin all directions. For 2D, this is a clear advantage over LCD displaysthat require a backlight and that, without taking special measures, emitlight only in a narrow beam. The diffuse emission of the OLED materialalso poses a challenge as a lot of light is recycled inside the organiclayers and is not emitted making for a low efficiency. For example,without taking any measures, the light extraction out of the OLED can beas low as 20%.

To improve this various solutions have been sought to improve theout-coupling of the light out of the OLED.

However, what is an improvement for 2D displays is a problem for making3D autostereoscopic OLED displays. The solutions for increasing thelight output cannot be used in autostereoscopic lenticular displays asthe light emitted from one lenticular lens may be reflected in the glassto a neighbouring lens. This reduces contrast and increases crosstalk.

FIG. 3 schematically shows the structure of a single pixel of an OLEDdisplay, and in the form of a backward emitting structure (i.e. throughthe substrate). Whilst OLED devices are typically bottom emitting asshown, and emit light through the glass substrate, another approach isto make the OLED stack top emitting such that the light emits through atransparent cathode (and a thin encapsulating layer) and not through theglass substrate.

In FIG. 3, the display comprises a glass substrate 30, a transparentanode 32, a light emissive layer 34 and a mirrored cathode 36.

The lines represent the path light can take when emitted from a point 38in the organic layer. As the light is emitted from the source it cantravel in all directions. When the light reaches the transition from onelayer to another layer the difference between the refractive index ofeach of the layers determines whether the light can escape one layer andget into the next. The refractive index is determined by the speed oflight in the material and is given by Snell's law:

$\frac{\sin \; \theta_{1}}{\sin \; \theta_{2}} = {\frac{v_{1}}{v_{2}} = \frac{n_{2}}{n_{1}}}$

v is the velocity and n is the refractive index.

Typically, the refractive index of the organic material is high n=1.8while the refractive index of glass is 1.45.

When the angle of incidence of light that travels from a material with ahigh refractive index to a material with a low refractive index is largeenough, the light cannot leave the material. This angle of incidence isthe critical angle and is given by a=arcsin(n2/n1). For the organicmaterial into glass this gives: arcsin(1.45/1.8)=54 degrees. This makesit evident that a lot of the light generated in the organic layer neverleaves the layer but stays inside the material, where it is re-absorbedand drives another photon emission or turns into heat.

The same happens for the light that does leave the organic layer andgets into the glass. A lot of light cannot leave the glass at the glassto air interface.

Several solutions have been proposed both for improving the coupling oflight out of the organic layers into the glass and out of the glass intoair.

Whilst traditional OLED devices emit light through the glass substrate,another approach as mentioned above is to make the OLED stack such thatthe light emits through a transparent cathode and a thin encapsulatinglayer and not through the glass substrate. This is referred to as a topemitting OLED. In general, different approaches to increasing the lightextraction work better (or only) with either top or bottom emitting OLEDstructures.

This invention is applicable to both the use of bottom- and top-emittingOLED displays.

Whilst known solutions help to improve the light extraction efficiencyup to 80% for lighting applications and for 2D displays, they do notprovide a good solution for an autostereoscopic 3D TV. A problem occurswhen fitting a lenticular lens on the OLED display for creating anautostereoscopic TV. Here, even with a top emitting OLED, light willstill be injected into a relatively thick glass layer causing theproblems highlighted above. Some of the known methods improve the lightextraction out of the organic material but a substantial amount of lightwill remain in waveguide mode in the glass, part of which will beabsorbed.

This has the undesired side effect of reducing contrast and increasingcrosstalk. This is more an issue for 3D displays because for 2Ddisplays, in many cases adjacent pixels will display the same colour(i.e. white or coloured areas of a screen, lines of single colour etc.)whereby if any light escapes from a neighbouring pixel, this will simplyadd to the desired colour. However, in a 3D display, adjacent pixels donot in general have any relationship to each other, as they belong todifferent views and will generally be of different colour content. Inthis case, if any light escapes from a neighbouring pixel, this willseriously affect the quality of the image.

FIG. 4 shows what in practice happens when applying a lenticular lens toa top emitting structure.

The display comprises the glass substrate 40, a reflective anode 42, theOLED layer 44 and the top transparent cathode 46. Pixels 45 are definedwith in the OLED layer by the pixel electrode design. A sealing andpassivation layer 48 is between the display and the lenticular lensarray 50. Even with out-coupling of all light from the display panelinto the lenticular array, there is still waveguiding within thelenticular array itself, which cannot be prevented by the known measuresto improve light out-coupling.

As illustrated in FIG. 4 some of the light will stay in waveguide modein the lenticular array glass and enter the optical path of aneighbouring view (or pixel/subpixel). Here it may be reflected back andleave through the lens or it is re-absorbed in the pixel. If the lightdoes leave the lens of the neighbouring view it will create somecrosstalk.

The invention provides the OLED emitters on a tilted surface withrespect to the general plane of the display, i.e. with respect to thedisplay substrate. In this way, each OLED pixel emits light centredaround a direction which is not perpendicular to the display, theemission direction being different for different pixels under a givenlens, and thereby different for regions of the lens surface throughwhich the pixel output is primarily directed. The out-couplingperformance is improved by arranging for the light emission direction tobe substantially perpendicular to the desired emitting surface of the(lenticular) lens array. The approach also results in a reduction ofcrosstalk between different views, as these become more separated inangle by the tilting.

FIG. 5 shows a first embodiment of a bottom emitting 3D OLED displaywith emitters tilted relative to display surface

In this first embodiment a bottom emitting OLED display structure isshown, and the OLED emitters associated with each lenticular lens havinggiven different angles of tilt of their light output surface relative tothe plane of the display surface.

The cross section of FIG. 5 (and the other figures) is vertical (i.e.perpendicular to the display plane) and along the lenticular lens widthdirection. The angle of tilt is in this plane. The lens elongate axisdirection is into or out of the page and is within the plane of thelight output surface.

The angle of tilt is in a plane perpendicular to the display substrateplane and parallel to the lens width direction (i.e. in a vertical slicethrough the display across the lens width direction). The lens elongateaxis direction remains parallel to the plane of the light outputsurface, so that the angle of tilt can be considered as a tilt about theelongate lens axis. The light output surfaces are thus tilted in a waywhich generally corresponds to (or mirrors) the shape of the lenssurface. In some cases, the tilt may also be in a plane perpendicular tothe display substrate plane and at an angle to the lens width direction.This may be a practical solution if, for example, the lenticular isaligned at an angle to the column direction of the display. The tilt canthen be in a plane perpendicular to the display substrate plane andperpendicular to the pixel column direction.

The OLED pixels are shown as 60. Their layer structure is conventional,for example as described above in connection with FIG. 3 or 4 and is notrepeated. The OLED pixels are on the underside of the main display glasssubstrate 62, with the lenticular lens array 64 on the opposite side ofthe substrate 62 to the pixels 60.

FIG. 5 (and the other figures) are not drawn to scale: typically, thethickness of the OLED layers are submicron, whereas the verticaldimensions of the lenticular lens are 100's-1000's of microns, and thelateral dimension of the pixels is the order of 100's of microns. Thusin practise, the tilt angle of the OLEDs will be lower than suggested bythe figures.

The angle of tilt depends for example on the angular width of the lenssurface. With the curved lens surface facing outwards, a maximum angleneeded is around 45 degrees. When the lens has a replica, the maximumangle that enters the lens is determined by the refractive index of theglass. For instance, when the glass has a common refractive index valueof n equal to 1.5, then the critical angle at the glass-air interface issin⁻¹(1/n), which equals 42 degrees. For an extreme value of n equals1.7 it gives 36 degrees and for n equals 1.3 it gives 50 degrees.

The extreme rays close to this critical angle are not typically in theprimary cone (see FIG. 2), so the maximum tilt angle can be less. Forcurrent products, the viewing cone angle is typically only 10 degrees sothat the approach of the invention is less critical. With OLEDtechnology providing increased resolution, cone angles will increase:making three times the views allows a cone of 30 degrees full-anglerelative to that the current typical design. In this case, some pixelemitters should be titled by 15 degrees.

The light rays are emitted centred around the direction perpendicular tothe OLED pixel output surface, but with a broad distribution. The widthof the distribution depends upon the details of the OLED stack. Thedesign is such that the centre of this distribution—where theintensities are highest—is perpendicular to the local exit surface. Inthe figures, only this central highest intensity output direction of thelight distribution is represented.

The tilt angles are designed such that the OLED light exits thelenticular lens surface at an angle close to perpendicular to the localexit surface of the lens. Thus, the light output surface of each OLEDpixel has a normal direction (the arrows shown in FIG. 5) which crossesthe lens surface perpendicularly to the local tangential surface to thelens. The tilt angle increases away from the centre of the lenticularlens in a symmetrical manner. In this manner, the light intensityemitted from the display is maximised. Furthermore, the tilt angle alsoreduces the amount of light which is emitted from a pixel in thedirection of its neighbour, whereby the amount of cross talk furtherreduces.

For manufacturing purposes, the tilt may be realised in several manners:

-   (i) using a planar OLED sheet which is later deformed, for instance    by laminating a flexible or conformal OLED sheet (such as realised    using a plastic (polyimide) or metal foil substrate) on a more rigid    preformed substrate;-   (ii) deposition of OLEDs on a pre-formed substrate. As the surface    topography required is limited both evaporation techniques (as used    for OLED deposition) and conventional surface processing techniques    (such as spin coating) are possible;-   (iii) Using a standard glass substrate and using a photo-resist    (such as SU8) or a dielectric layer (such as SiO₂), or a combination    thereof to form tilt structures.

Experience of forming such layers within display processing has beenobtained from LCD's with so-called field shielded pixels, fromtransflective LCDs (where the cell has 2 different LC cell gaps) and forgenerating printing dams for polymer OLED displays.

A second embodiment is shown in FIG. 6 using a top emitting OLED displaystructure with emitters tilted relative to the display surface.

The OLED pixels are again shown as 60. The OLED pixels 60 are on theupper side of the main display glass substrate 62, with the lenticularlens array 64 over the pixels 60. Again, the OLED emitters havedifferent tilts relative to the plane of the display surface. In thesame way as in the embodiment of FIG. 5, the light rays are emittedcentred around the direction perpendicular to the OLED pixels, and exitthe lenticular lens at an angle close to perpendicularly to the localexit surface.

One issue related to this embodiment is the in-coupling of light intothe lenticular lens since it is desirable to avoid internal reflectionat the lower boundary of the lenticular structure. This can be improvedby the use of a collimated OLED emitter, by a local (tilted) in-couplingfacet on the underside of the lenticular lens, or by using a medium ofintermediate refractive index between the emitter and the lens.

The same manufacturing options are available as discussed above.

FIG. 7 shows a variation in which the tilted OLED emitters 60 arepositioned across a concave contoured surface 70 positioned directlyunder the (convex) lenticular lens 64.

In this case an additional benefit is that all OLED pixel emitters canbe brought into focus simultaneously. In particular, the pixels acrossthe lens width direction are arranged with different heights over thesubstrate, so that they can be positioned closer to the focalcurve/surface of the lenticular lens. Thus, the pixels are preferablypositioned at heights corresponding to the focal surface of thelenticular lens. This can also be achieved in the embodiment of FIG. 6by suitable design of the height as well as orientation provided to thepixels. In this way, all pixels below the lenticular lens are broughtinto focus by varying the spacing between the substrate and the tiltedemitters in a repeating manner across the lenticular lenses. In the caseof a top emitting structure, the spacing increases towards the edge ofeach lenticular lens.

As mentioned above, collimating OLED emitters can be used, and FIG. 8shows a modification to FIG. 7 to show schematically the use ofcollimated OLED pixels 60.

The designs above are intended to provide the best viewing experiencewithin the primary cone (explained above with reference to FIG. 2). Asshown in FIG. 9, for oblique angles and therefore for lateral(secondary) viewing cones, light is emanating from a reduced set ofpixels, representing a reduced set of views, and thus the parallax andthereby the 3-D effect is reduced. In FIG. 9, a light ray from thesecond pixel in from the edge of the lens area is shown, which is a blue(sub) pixel. The edge pixel which is shown as green will not contributeto secondary viewing cones to the left, whereas all pixels for a flatdisplay panel will contribute to secondary viewing cones to each side.This may be well acceptable for some applications, but for single-userdevices it may be better to reduce the viewing range to the primarycone.

This can be achieved by blocking unwanted rays of light for example byusing blocking structures between the lenses, and it is even possiblemake this choice adaptive.

An alternative is to design the optics so that a full single conesolution is provided. For example. the output from a single cone canspan the full 180 degrees, or else a smaller angle such as 120 degreeswith no viewing beyond this single cone. region. A single cone solutioncan for example use the techniques described in WO-2009/147588. For asingle cone display the outermost views will still not have a very goodquality so the optical design should be optimized on the inmost 45degrees to 90 degrees for example.

It is noted that the curvature of the tilted emitters can be adjusted tocorrect for monochromatic aberrations.

Outside of a zone with proper view separation, the stereoscopic cue islost but the motion parallax cue can be preserved. However it may bebetter to create a left and right 2D region if 3D information is lackingin the content. This allows the use of big emitters for the 2D regionsand reduces some of the complexity of the active matrix and otherdisplay electronics.

The display can comprise any electroluminescent display technology, suchas PLEDs (polymer LEDs) or OLEDs (organic LEDs).

The technology used to form the display pixels is not changed byimplementing the invention. Similarly, the lenticular lens design is notaltered. Instead, the tilts are used to modify the pixel layout to besuitable for the lenticular design.

As mentioned above, the tilt angle is relatively small, and also anydesired height offset is a fraction of the pixel width, so that theprocessing is not complicated.

The display will typically comprise an active matrix display, with driveelectronics associated with each display pixel, for switching a drivecurrent to selected pixels. This can be carried out in routine mannerand is not affected by the invention. For this reason, the driveelectronics is not shown or described in detail. The connections to thepixel anodes and cathodes need to step up the height differences, orelse vias can be used to connect to the different-height pixelterminals.

The examples shown schematically above have four or five pixels underthe width of the lens. The number of pixels beneath each lens dictatesthe number of views as well as viewing cones of the display, and theremay be more or less, for example 3, 9 or 11. In general, there are atleast two pixels per lens width.

The pixel pitch is slightly larger than the lens pitch, so that thepixels effectively wrap around the lenticular screen to create the pairof views in the ideal viewing direction.

There can be at least three pixels per lens width for a multi-viewsystem.

The lens pitch can be a non-integer multiple of the pixel pitch, and inthis case the viewing cones are distributed over adjacent lenses.

The examples above make use of lenticular lenses as the view formingarrangement. However, an array of microlenses can also be used. Eachmicrolens again covers a set of pixels in the width (i.e. row) directionand the different pixels have different tilt orientations. The microlenswill in general also display a curvature in the column direction. Ifassociated with more than one pixel in the column direction, thedifferent pixels have different tilt orientations across the width ofthe lens in the column direction—whereby the view forming elementessentially consists of two distinct width directions. Typically, thetilt direction of these pixels will be in a plane perpendicular to theplane of tilt of the pixels in the row direction. Furthermore, there maybe pixels associated with the corners of the microlenses where the planeof tilt is intermediate between the other pixels. In the columndirection, each microlens can be associated with one or more pixels. Theexample of a lenticular lens can be considered to be a microlensextended to the extreme of covering a full column of pixels.

The invention can be applied to 3D displays as used in TVs, tablets andphones.

Other variations to the disclosed embodiments can be understood andeffected by those skilled in the art in practicing the claimedinvention, from a study of the drawings, the disclosure, and theappended claims. In the claims, the word “comprising” does not excludeother elements or steps, and the indefinite article “a” or “an” does notexclude a plurality. The mere fact that certain measures are recited inmutually different dependent claims does not indicate that a combinationof these measured cannot be used to advantage. Any reference signs inthe claims should not be construed as limiting the scope.

1. An autostereoscopic display device comprising: a display comprisingan array of electroluminescent pixels disposed over a substrate, thearray of electroluminescent pixels having rows and columns, wherein therows are disposed in a width direction and the columns are disposed in aheight direction, wherein each pixel has a light output surface, and anautostereoscopic view forming arrangement comprising a set of viewforming elements disposed over the display, wherein a portion of thearray of electroluminescent pixels is provided beneath each view formingelement wherein at least two electroluminescent pixels are arrangedacross each of the view forming elements in the width direction, whereinthe at least two electroluminescent pixels arranged across each of theview forming elements in the width direction are arranged to have atleast two different angular orientations of the light output surfaceswith respect to the substrate, wherein the electroluminescent pixels aredisposed between the substrate and the view forming arrangement.
 2. Theautostereoscopic display device as claimed in claim 1, wherein theportion of the array of electroluminescent pixels beneath each of theview forming elements comprises at least three electroluminescent pixelsacross each of the view forming elements in the width direction.
 3. Theautostereoscopic display device as claimed in claim 1, wherein the viewforming arrangement comprises an array of lenticular lenses.
 4. Theautostereoscopic display device as claimed in claim 3, wherein theelectroluminescent pixels are positioned at heights corresponding to thefocal surface of the lenticular lens.
 5. The autostereoscopic displaydevice as claimed in claim 3, wherein the lenticular lenses extend inthe height direction or are inclined at an acute angle to the heightdirection, wherein each lens covers a plurality of columns.
 6. Theautostereoscopic display device as claimed in claim 1, wherein thedisplay comprises: an array of reflective anodes disposed over thesubstrate; an array of electroluminescent layer portions disposed overthe anodes; and an array of transparent cathodes disposed over theelectroluminescent layer portions.
 7. The autostereoscopic displaydevice as claimed in claim 1, wherein the substrate is planar, whereinthe device comprises spacers between the substrate and at least some ofthe electroluminescent pixels, wherein the spacers define different tiltangles.
 8. The autostereoscopic display device as claimed in claim 1,wherein the substrate is planar, wherein the device comprises spacersbetween the substrate and at least some of the electroluminescentpixels, wherein the spacers define different pixel heights with respectto the substrate.
 9. The autostereoscopic display device as claimed inclaim 1, wherein the substrate has a non-planar shape, wherein thenon-planer shapes defines different tilt angles at a substrate surface.10. An autostereoscopic display device comprising: a display comprisingan array of electroluminescent pixels disposed over a substrate, thearray of electroluminescent pixels having rows and columns, wherein therows are disposed in a width direction and the columns are disposed in aheight direction, wherein each pixel has a light output surface, and anautostereoscopic view forming arrangement comprising a set of viewforming elements disposed over the display, wherein a portion of thearray of electroluminescent pixels is provided beneath each view formingelement wherein at least two electroluminescent pixels are arrangedacross each of the view forming elements in the width direction, whereinthe at least two electroluminescent pixels arranged across each of theview forming elements in the width direction are arranged to have atleast two different angular orientations of the light output surfaceswith respect to the substrate, wherein the substrate is disposed betweenthe electroluminescent portions and the view forming arrangement. 11.The autostereoscopic display device as claimed in claim 10, wherein theportion of the array of electroluminescent pixels beneath each of theview forming elements comprises at least three electroluminescent pixelsacross each of the view forming elements in the width direction.
 12. Theautostereoscopic display device as claimed in claim 10, wherein the viewforming arrangement comprises an array of lenticular lenses.
 13. Theautostereoscopic display device as claimed in claim 12, wherein theelectroluminescent pixels are positioned at heights corresponding to thefocal surface of the lenticular lens.
 14. The autostereoscopic displaydevice as claimed in claim 12, wherein the lenticular lenses extend inthe height direction or are inclined at an acute angle to the heightdirection, wherein each lens covers a plurality of columns.
 15. Theautostereoscopic display device as claimed in claim 10, wherein thedisplay comprises: an array of transparent anodes disposed over thesubstrate; an array of electroluminescent layer portions disposed overthe anodes; and and an array of reflective cathodes disposed over theelectroluminescent layer portions.
 16. The autostereoscopic displaydevice as claimed in claim 10, wherein the substrate is planar, whereinthe device comprises spacers between the substrate and at least some ofthe electroluminescent pixels, wherein the spacers define different tiltangles.
 17. The autostereoscopic display device as claimed in claim 10,wherein the substrate is planar, wherein the device comprises spacersbetween the substrate and at least some of the electroluminescentpixels, wherein the spacers define different pixel heights with respectto the substrate.
 18. The autostereoscopic display device as claimed inclaim 10, wherein the substrate has a non-planar shape, wherein thenon-planer shapes defines different tilt angles at a substrate surface.